About Brass Mutes
While certain brass mutes suppress an instrument's sound most of them do not - many brass mutes affect the pitch of the instrument they're fitted to. Mutes either slide into the bell of the instrument are used by hand or clipped out of the lip of the horn. These accessories are made from aluminum brass or a copper/metal alloy with more economical options being plaster plastic and even cardboard. Each material produces its own unique pitch so players should experiment with a few different models and styles to see (and hear) which brass best mute complements their musical style.
A straight mute is the most common type of mute used by brass musicians. It's a hollow cone-shaped mute with a small piece of cork attached to the end to keep it secure in the bell of the instrument. Its sound is described as metallic and piercing. Cup mutes like the Jo-Ral 6L Standard Tenor Trombone Cup Mute produce more muffled darker tones due to the cup piece that's attached to the end of the mute's cone. Plunger mutes like their name suggests look like plungers with their handles removed. The musician manipulates a plunger mute by holding it in front of the bell. Stop mutes are designed specifically for the French horn. Hand-stopping involves the musician putting a closed fist into the bell of the instrument to cut off the airflow resulting in a buzzing sound. This technique is said to be very difficult but can be made much easier with a stop mute like the Denis Wick DW5525 French Horn Stop Mute.